1. Field of the Invention
The present invention relates generally to hazards classification of energetic materials and other explosive ordinance. More particularly, the present invention relates to a propane fueled combustion device which provides a controlled heat flux environment for hazardous classification of an ordinance system.
2. Description of the Prior Art
In the United States, all ordnance must be hazard classified. Hazards classification of an energetic material (which are used in all ordnance systems) requires a number of tests to determine the type of reaction and level of reaction violence for various potential accident scenarios in transport and storage situations. These tests include shock initiation, sympathetic detonation, and external fuel-fires which are referred to as cook-off tests. Both shock initiation and sympathetic detonation tests have small-scale analog tests that allow for alternative options to expensive full-scale testing.
To date, no small-scale test has or exists or is under development for the external fuel-fire test required for classification of explosive ordnance. A test of this type can be very expensive for rocket motors greater than 11 inches in diameter as it requires the use of three full-sized, production assets or rocket motors in their shipping and storage configuration.
For a liquid fuel/external fire test, a rocket motor is exposed to a liquid fuel fire, which extends a maximum of one meter beyond the edge of the motor. There is also a requirement that the fuel burn for 150 percent of the time required to cause a reaction. The initial cost of the rocket motor, the potential hazards associated with conducting the test, and the amount of land required for a test site are some of the difficulties in performing an external fire test on a solid rocket motor.
For large-scale rocket motors, it is highly likely that performing a full-scale fuel-fire test will be cost prohibitive. Furthermore, the physical nature of a fuel-fire is very difficult to quantify and measure. Understanding how heat flux is coupled from the fuel-fire flames to a specific device, such as a large scale rocket motor is important to experimental and computational modeling efforts in this area.
Currently for hazard classification, the Department of Defense Explosives Safety Board mandates that full-scale external fuel fire tests are performed using a shallow pool of aircraft fuel (JP-5 or JP-8 jet fuel) and a minimal amount of instrumentation to determine the air temperature at several locations. This type of full-scale fuel fire testing is difficult to perform because it requires the use of a full-scale test specimen and large specialized facilities, both of which can be extremely expensive. The full-scale test is capable of providing the necessary thermal stimulus, but it lacks sufficient instrumentation to quantify the stimulus for use in present day computational models. Technology is not currently available to provide the necessary resolution of measured heat flux level or provides a sufficient level of control for the application of constant thermal boundary conditions into a small-scale/smaller than full-scale test specimen for the purpose of observing the resulting response of the energetic material. Accordingly, there is a need for a small-scale external fuel fire test apparatus for hazard classification and also to probe the underlying physical response of energetic materials to fast cook-off in a controlled manner.